title: Effect of different etching periods on the bond strength of a composite resin to a machinable porcelain.
abstract: OBJECTIVE
  The purpose of this study was to evaluate microstructure changes of Cerec 2 Vitablocs Mark II porcelain etched by a 5% hydrofluoric acid and examine the effect of different etching times on the bond strength between the porcelain and a composite resin.
  
  
  METHODS
  Six different etching times (0, 5, 30, 60, 120 and 180 s) were used to etch the surfaces of the porcelain, respectively. Etched relief patterns were observed by means of a scanning electron microscope and the bond strength was determined between a dual-cured composite luting agent and the porcelain.
  
  
  RESULTS
  The results showed that composite resin did not bond to unetched porcelain but bonded to etched porcelain, the 120 s etch giving the highest bond strength.
  
  
  CONCLUSIONS
  The bond strength values corresponded well to the microstructure changes caused by etching.
authors.affiliation: Department of Fixed Prosthodontics, Nagasaki University School of Dentistry, Japan.
authors.forename: J H
authors.initials: JH
authors.lastname: Chen
authors.forename: H
authors.initials: H
authors.lastname: Matsumura
authors.forename: M
authors.initials: M
authors.lastname: Atsuta
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods*; D000704:Analysis of Variance; D002516:Ceramics / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003776:Dental Porcelain / Q000737:chemistry*; D004868:Equipment Failure; D005069:Evaluation Studies as Topic; D006858:Hydrofluoric Acid / Q000737:chemistry; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors
chemical_list: D003188:Composite Resins; D003776:Dental Porcelain; C074543:Cerec; D006858:Hydrofluoric Acid